9-OXO-11ALPHA,16R-DIHYDROXY-17-CYCLOBUTYL-5Z,13E-DIEN-1-OIC ACID

Butaprost is a structural analog of prostaglandin E₂ (PGE₂) with good selectivity for the EP₂ receptor subtype. Butaprost binds with about 1/10 the affinity of PGE₂ to the recombinant murine EP₂ receptor, and does not bind appreciably to any of the other murine EP receptors or DP, TP, FP, or IP receptors.¹ CAY10408 is a free acid, 2-series analog of butaprost. It is the less active C-16 epimer compared to the 16(S) isomer, which has the same stereochemistry as butaprost. Butaprost has frequently been used to pharmacologically define the EP receptor expression profile of various human and animal tissues and cells.² Since the majority of reports related to butaprost utilize the methyl ester derivative,^3,4 it may be some time before the precise pharmacology of the free acid compounds, like CAY10408, is reported.

1. Kiriyama, M., Ushikubi, F., Kobayashi, T., et al. Ligand binding specificities of the eight types and subtypes of the mouse prostanoid receptors expressed in Chinese hamster ovary cells Br. J. Pharmacol. 122(2),217-224(1997).
2. Lawrence, R.A., and Jones, R.L. Investigation of the prostaglandin E (EP-) receptor subtype mediating relaxation of the rabbit jugular vein Br. J. Pharmacol. 105,817-824(1992).
3. Regan, J.W., Bailey, T.J., Pepperl, D.J., et al. Cloning of a novel human prostaglandin receptor with characteristics of the pharmacologically defined EP₂ subtype Mol. Pharmacol. 46(2),213-220(1994).
4. Talpain, E., Armstrong, R.A., Coleman, R.A., et al. Characterization of the PGE receptor subtype mediating inhibition of superoxide production in human neutrophils Br. J. Pharmacol. 114(7),1459-1465(1995).